Narrowband and wideband EMW path loss in underwater wireless sensor network

Purpose Utilization of electromagnetic wave (EMW) sensors in an underwater environment has the potential to increase the data rate compared to acoustic-based sensors because of the ability to use larger signal bandwidth. Nevertheless, EMW signals has the drawback of large signal attenuation in underwater, attributed to the high relative permittivity and conductivity of water compared to the atmosphere, hence employment of wide signal bandwidth is necessary to balance the data rate-attenuation trade-off. The purpose of this paper is to analyze the characteristics of both narrowband and wideband EMW signal propagation underwater and devise a path loss model for both cases. Design/methodology/approach Path loss measurement was conducted using a point-to-point configuration in a laboratory water tank while transmitting narrowband and wideband signals between a pair of wideband underwater antennas. The wideband underwater antennas use buffer-layer structures as the impedance matching layer to optimize the antenna performance when operating underwater. The path loss for narrowband signal was modeled using a multi-layer propagation equation in lossy medium considering losses at the medium boundaries. For the case of the wideband signal, a modified version of the model introducing power integration over bandwidth is adopted. These models were formulated through numerical simulations and verified by measurements. Findings The measured narrowband path loss marked an 80 dB attenuation using 800 MHz at 2 m distance. The proposed narrowband model agrees well with the measurements, with approximately 3 dB modeling error. Utilization of the proposed wideband path loss model resulted in a reduction of the gradient of the path loss curve compared to the case of the narrowband signal. The measured wideband path loss at 2 m distance underwater was approximately −65 dB, which has been shown to enable a working signal-to-noise ratio of 15 dB. This proves the potential of realizing high data rate transmission using the wideband signal. Originality/value The paper proposed a wideband propagation model for an underwater EMW sensor network, using power integration over bandwidth. The effectiveness of using wideband EMW signals in reducing path loss is highlighted, which is seldom discussed in the literature. This result will be of useful reference for using wideband signals in designing a high data rate transmission system in underwater wireless sensor networks, for example, in link budget, performance estimation and parameter design of suitable transmission scheme.

A Bidirectional Hybrid WDM-PON with High Data Rate Transmission for Wired and Wireless Users in Long-Reach with Enriched Noise Tolerance Capacity against Rayleigh Backscattering

Transportation of 10 Gbps, 10 Gbps/40 GHz, 10 Gbps/200 MHz data for downlink (DL) and 6 Gbps data for uplink (UL) transmission with Rayleigh backscattering (RB) noise mitigation for wired and wireless users even in radio-frequency sensitive areas have been proposed and investigated. A 2×2 wavelength-division-multiplexing mux/demux is employed to separate DL and UL to avoid RB noise. Power penalty of < 1 dB at Bit error rate value of 10−9 and clear eye-diagrams express the reliability and fruitfulness of the proposed network.

A Bidirectional Hybrid WDM-PON with High Data Rate Transmission for Wired and Wireless Users in Long-Reach with Enriched Noise Tolerance Capacity against Rayleigh Backscattering

Transportation of 10 Gbps, 10 Gbps/40 GHz, 10 Gbps/200 MHz data for downlink (DL) and 6 Gbps data for uplink (UL) transmission with Rayleigh backscattering (RB) noise mitigation for wired and wireless users even in radio-frequency sensitive areas have been proposed and investigated. A 2×2 wavelength-division-multiplexing mux/demux is employed to separate DL and UL to avoid RB noise. Power penalty of < 1 dB at Bit error rate value of 10−9 and clear eye-diagrams express the reliability and fruitfulness of the proposed network.

Higher Data Rate Transmission for Underwater Wireless Sensor Communications Using Industrial, Scientific, and Medical (ISM) Bands

It is known that for underwater communication systems, lower frequency bands are used, which also affects the data rate transmission at lower rate. This is due to different physical phenomena such as reflections, refraction, and energy dispersion. This can be mitigated by installing wireless sensors that are placed close to each other, and hence, for accurate measurements, higher communication bandwidth is required. By using real scenario for measurement at higher data rate, 2.4GHz ISM band is used efficiently for underwater communication system with efficient use of energy.

Block diagonalization precoding and power allocation for clustering small-cell networks

The clustering network is a solution to improve data-rate transmission in small-cells. In this case, clustering small-cells (CSCs) adopt a multiple antennas concept. The multiple antennas are used to maximize the downlink data-rate transmission at the users, but it requires precoding techniques to minimize interference among CSC users. This paper proposes a block diagonalization (BD) as a precoding technique for minimizing interference among CSC users. The performance of the BD precoding implemented on the clustering network under various numbers of small-cells. The CSC also implements a water-filling power allocation (PA-CoopWF) to distribute the available transmission power along with the CSCs antennas. To show the performance, our paper simulates two types of precoding techniques; those are the proposed BD and minimum mean square error (MMSE) in CSCs. Based on the receiver user parts under the overlapping coordination of CSCs, our method based on the BD precoding achieves considerably higher data-rate transmission compared to the MMSE precoding, especially on larger clusters. The simulation also shows that by implementing CSC with the BD in short-range distances and higher numbers of antennas, it promotes better data-rate performances compared to the MMSE precoding by 2.75 times at distance 100m and 67% at 50 antennas.

Feasibility of Backscatter Communication Using LoRAWAN Signals for Deep Implanted Devices and Wearable Applications

This paper presents a method for low data rate transmission for devices implanted in the body using backscattered Long Range (LoRa) signals. The method uses an antenna loaded with a switch that changes between two load impedances at the rate of a modulating oscillator. Consequently, the LoRa signal transmitted by a LoRa node is reflected in the adjacent channels and can be detected with a LoRa gateway tuned to the shifted channels. A prototype developed to operate at Medical Implant Communication Service (MICS) and the Industrial Scientific and Medical (ISM) 433 MHz band is presented. The prototype uses a commercial ceramic antenna with a matched network tuned to the frequency band with high radiation efficiency. The effect of the coating material covering the antenna was studied. Simulated and experimental results using a phantom show that it is feasible to read data from deep implanted devices placed a few meters from the body because of the high sensitivity of commercial LoRa receivers.

Performance analysis of FSO link under the effect of fog in Delhi region, India

Fog attenuation causes more loss than other weather conditions in a free space optics (FSO) link thus limiting the visibility distance. This work presents a detailed survey on the attenuation of the transmitted signal as a result of variation in visibility range caused by different fog conditions of the Delhi, Safdarjung region. Kim and Kruse models have been used to calculate attenuation as a result of fog conditions for three specific months (January, February and December) for seven consecutive years starting from 2013 to 2019. Received signal quality has been analyzed as a function of transmitted power, data rate, transmission range and operation wavelength. Descriptive statistical analysis of real time observed visibility data allows for the estimation of specific optical attenuation and enables in determining the link availability of the region for the complete year.